This invention relates to an improved alkaline dry cell comprising in combination a zinc anode, a silver oxide cathode and an alkaline electrolyte, and in particular an improvement in a cathode for the alkaline dry cell.
A conventional dry cell contains a silver oxide (Ag.sub.2 O) as an active ingredient. In such a conventional dry cell, a silver oxide is a poor non-conductor showing, for example, a greater resistance of about 10.sup.8 .OMEGA.cm. For this reason, an electroconductive ingredient such as graphite is added to a silver oxide, as shown in U.S. Pat. No. 3,427,204 so as to enhance electroconductivity. In order to obtain necessary electroconductivity from the standpoint of the characteristic of the dry cell, use is generally made of a cathode obtained by compressing a composition comprising 95 parts of silver oxide, 4.5 parts of graphite and 0.5 part of a binder under a pressure of 5 to 10 ton to form a pellet or a compressed coherent mass. The use of the graphite reduces an amount of silver oxide by that extent, when viewed based on the whole weight of the composition, resulting in a decreased discharge capacity. Therefore, difficulty is encountered in attaining high performance of a compact button type cell of closed variety in particular. Graphite shows a resistance of about 10.sup. .sup.-2 .OMEGA.cm. Since a great difference of resistance is observed between the graphite and the silver oxide, it is necessary to form a pellet by uniformly mixing each ingredient of the composition and compressing the mixture under a pressure. In actual practice, however, many difficulties are involved, since the graphite is smaller in true specific gravity than the silver oxide.